In order to save water resources, existing toilets are mostly siphon-type toilets which bring sewage out of the toilet bowl through siphonage formed during water drainage with strong ability of sewage discharge, and they are more water-saving than ordinary wash-down toilets. Flushing structures of existing siphon-type toilets generally comprise a jet waterway to directly eject towards the inlet of the sewage discharge waterway at the bottom of the toilet bowl to assist in formation of siphonage. However, as most jet waterways are in communication with a rim waterway for flushing the inner wall of the toilet bowl, air will enter the jet waterway through the rim waterway, and during water drainage, air in the jet waterway needs to be exhausted first, so as to form siphon-type drainage to speed up drainage. In order to solve the abovementioned problem, in the prior art, there is a solution of providing a check valve between the jet waterway and the rim waterway to prevent air from entering the jet waterway through the rim waterway after drainage. However, the check valve on the toilet has a small mounting space and is difficult to mount, the structure of the toilet is complex and it costs much. There is another technical solution of using separate jet waterway and rim waterways which are not in communication to solve the abovementioned problem. However, such technical solution needs two drain valves to respectively control the on and off states of the jet waterway and rim waterway, two drain valves cost much and ceramic production technology of two separate waterways are complex. Besides, there is also a technical solution of using a water seal structure to prevent air from entering the jet waterway through the rim waterway after drainage. However, most flushing waterways of toilets having a water seal structure have a complex structure, ceramic production technology is also complex, much modification of the inner structure of the toilet is involved, which results in high cost of modification. Moreover, for existing flushing waterways of toilets having a water seal structure in the market, some provide the inlet of the rim waterway nearby the jet hole, or although the inlet of the rim waterway is not provided nearby the jet hole, there is no enough upward section between the jet hole and the inlet of the rim waterway, such that during flushing, polluted water nearby the jet hole will be flushed into the rim waterway and flow out of a rim hole, causing a problem of secondary pollution of the toilet bowl or even blocking of the rim hole by sewage.